Happy Birthday

Bit of a short one this time, but if you ever attended a university maths class, you may have been asked:

How many people do you need in a room to have a good chance that at least two of them share the same birthday?

On first glance, you would think that with 365-ish possible dates, we would need at least 366 people to guarantee that. Therefore you would probably need half of that for a 50% chance right? Nope.

In fact, in a group of 23 randomly chosen people, the chance is slightly higher than 50 percent that two will share a birthday.^[1]